SNMP Series: SNMP Monitoring in Operations Manager and Essentials 2007 (Part 1)
SNMP is a bit unfamiliar to many OpsMgr and Essentials administrators, so as promised, we’re going to deliver a series in which we unravel the SNMP functionality in both platforms, from basic concepts to advanced monitoring functionality. As Confucius said, “a journey of a thousand miles begins with a single step”. So let’s start at the beginning.
In the first installment of our SNMP Series, we’ll begin unraveling the mystery around SNMP by answering the question What is SNMP?
The short answer is, The SNMP protocol is an industry standard protocol used by network management systems (NMS) to communicate with network elements.
NOTE: For purposes of our discussion, the NMS is Operations Manager or Essentials 2007, and the network elements are SNMP-enabled network devices we have targeted for monitoring by discovering them through the Discovery Wizard. There are some nuances to this statement, but we’ll split hairs later.
There are a few terms relating to SNMP monitoring that we’ll be hear repeatedly during the series, so let’s get these out of the way.
Important SNMP-related Terms
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SNMP TRAP is a message which is initiated by a network element and sent to the network management system. For example, a router could send a message if one of its redundant power supplies fails or a printer could send an SNMP trap when it is out of paper. Operations Manager or Essentials can be configured as an SNMP trap receiver to catch traps from discovered network devices. More on this in a future post.
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Variable Binding - Contents of an SNMP trap. The trap contains an SNMP Object Identifier and it’s value. This OID/value pair is called an SNMP variable binding, or simply varbind.
The NMS can read values (by issuing a GET) or change values (SET) on the agent
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SNMP GET is a message which is initiated by the network management system when it wants to retrieve some data from a network element. Operations Manager and Essentials can be configured to perform an SNMP GET to retrieve a value from a network device and make a determination of health based on the value retrieved, but that’s not all we can do with that data. You guessed it…more on this in a bit.
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SNMP SET is a message which is initiated by the NMS when it wants to change data on a network element. For example, the NMS may wish to alter a static route on a router.
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SNMP MIB, or Management Information Base, is a collection of variables which is shared between the NMS and the network element (NE). Think of a MIB as an address book of all of the object and attributes in an SNMP-enabled network device. The addresses in the MIB are called Object Identifiers, or OIDs. Operations Manager and Essentials do not use MIBs directly, but MIBs are very important, because they contain OIDs. These are essential in all flavors of SNMP monitoring in OpsMgr and Essentials.
- OBJECT IDENTIFIER (OID) - The OID defines the attribute of our device that we can GET or SET to retrieve a specific value. The MIB provides the name, OID, data type, read/write permissions and a brief description for each object in our network device. An OID is a list of numbers separated by periods. For example, the OID for the Name of a SNMP-enabled device is .1.3.6.1.2.1.1.5.0.
- COMMUNITY STRING The most basic form of SNMP security is the Community String. SNMP Community Strings are like passwords for network elements. Most often, there is one community string which is used for read-only access to a network element. The default value for this community string is often “public”. Using this community string like a password, the NMS can retrieve data from network elements. We need to know the READ community string in order to cover our SNMP-enabled network devices in Operations Manager and Essentials 2007.
With these basic concepts out of the way, we’re ready to start talking about SNMP in the context of Operations Manager and Essentials. In part 2, we’ll drill down on SNMP device discovery and availability monitoring in both Operations Manager and Essentials. I’ll stop here and we’ll pick up with that topic Part 2 of our series on Monday.
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